a) Field of the Invention
The present invention relates to a penetration bending method and a bending machine for carrying out said method, more specifically to a simple penetration bending method which is applicable to plastic works for manufacturing various types of bent parts by using hollow pipes, sections and solid pipes (hereinafter referred to as rod-like members),and permit freely bending the rod-like members with high precision, as well as a bending machine for carrying out said method.
b) Description of the Prior Art
Bent parts of pipes, etc. are utilized in various fields for manufacturing pipings, transportation appliances, domestic electrical products, mechanical structures, etc., and will find more fields of application the future. In order to manufacture the bent parts of the rod-like members to be used in the fields mentioned above, it is conventional to adopt the basic bending methods such as press bending, roll bending and so on.
Under the current circumstance where the bent parts are finding wider fields of application, it is demanded to lower the cost required for the bending works, enhance bending precision and obtain rod-like member which are bent continuously and complicatedly for logically building the rod-like members into narrow spaces reserved in various types of structures.
In order to satisfy these demands, the inventor proposed, as a method for bending pipes or sections with high precision, the bending method which was characterized by performing drawing or extrusion molding of pipes or sections in a condition where the bearing portion of a die restrainedly bearing a portion of a rod-like member is inclined relative to the feeding direction of pipe or section (Japanese Preliminary Patent Publication No. Sho 62-264137).
However, the conventional bending methods hardly permit, due to the mechanical engineering factors inherent therein, to enhance bending precision to the levels of specifications required for bent parts and are applicable only to simple bending works. Further, it is pointed out that the conventional bending methods have a common disadvantage or inconvenience to require relatively large bending mechines even for simple bending works. In addition, the method proposed by Japanese Preliminary Patent Publication No. Sho 62-264137 permits adequately enhancing bending precision, but requires performing delicate rotational control of a die and produces a certain difficulty in composing a bending machine for carrying out the method.